Intraocular Foreign Bodies (Cont’d)
Intraocular metallic foreign body imbedded in the inferior posterior eye wall. Note the “acoustic shadowing” in the orbital fat pads. (Modified from William Jones, OD).
The search for and identification of foreign bodies is extremely time-consuming compared with routine ocular diagnosis. Sometimes, foreign bodies are surrounded by hemorrhage. The sensitivity then has to be reduced so that the hemorrhage is not seen. Varying the sensitivity permits differentiation of high-amplitude echoes produced by most foreign bodies from lower-amplitude echoes emanating from the surrounding hemorrhage.
Magnetic foreign bodies can be identified using an ultrasonic display of the motion of the foreign body when a magnet is applied to the globe, placed in a position over the pars plana. Foreign bodies of glass, plastic, and wood require serial sections for exact localization.